Electric utilities require information concerning the electric consumption of typical appliances for use in load forecasting and for planning future generation and transmission capacity. Public policy makers also require such information for their guidance in rate setting and reviewing capacity expansion plans.
The energy consumption of any particular appliance can be measured readily in a laboratory, but this does not necessarily indicate the energy consumption of the appliance in typical use. For example, the energy consumption of a refrigerator in a household wherein the door may be frequently opened may be vastly different than under laboratory conditions. Laboratory testing also does not indicate the energy consumption of the existing mix of new and old refrigerators which may be operating in any particular geographical region. It is the energy consumption of appliance classes (e.g. all refrigerators or all water heaters), and their trends, that utilities are most interested in obtaining.
To collect this information, utilities typically select one to two hundred houses in a region, and monitor the electric consumption of the major appliances in each house. They then combine the information from the individual appliances together statistically to calculate the consumption of each class of appliance. Two methods are currently available for measuring the energy use of individual appliances in normal operation: The "Electric ARM" and New England Electric Systems's "MATREC" system. Both of these systems are described in Proceedings: EPRI Load Research Symposium, Electric Power Research Institute, Palo Alto, 1984. These systems are limited in the number of appliances they can monitor and, more importantly, they have the disadvantage of requiring electric utility personnel to enter the premises and connect sensors to individual appliances or the circuits feeding them. This is clearly undesirable as it disturbs the residents and may result in assumption by the utility of liability in respect to the home-owner owned wiring.
Accordingly, a need exists for a relatively low cost, versatile apparatus and method for monitoring and recording the energy consumption of individual appliances within a residence which may be installed external to the residence without requiring physical intrusion into the residence.